1. Field of the Invention
The invention relates to dual-band antennas. More specifically, in a preferred embodiment, the invention relates to a cost efficient antenna tunable for use with both 802.11a and 802.11b/g “Wi-Fi” frequency bands.
2. Description of Related Art
Digital wireless systems, for example wireless local area computer networks, utilize frequency bands allocated for use by specific communication protocols. To provide users with increased connectivity options, it is desirable to provide multiple protocol capability. Because the standardized “Wi-Fi” protocols are not allocated to frequency bands that are harmonically related to each other, it has been difficult to provide a cost effective single antenna solution with acceptable dual band performance.
Sleeve chokes are a known method for tuning a whip and or dipole antenna. Typically the choke is a ¼ wavelength sleeve a distal end coupled to an outer conductor of a coaxial feed or a proximal end of the inner conductor. The inner conductor of the coaxial feed forms an antenna element that extends beyond the sleeve for ¼ wavelength of the target frequency. Because the choke and the extending antenna element are both ¼ wavelength of the target frequency, it is difficult to tune the resulting antenna to dual bands that are not harmonically related.
To achieve acceptable dual band performance, prior dual band antenna configurations have used multiple concentric and or mechanically interconnected at one end sleeve/choke assemblies. However, these configurations have increased cost and manufacturing tolerance requirements. Further, the resulting antenna has an increased diameter to accommodate the additional concentric sleeve(s).
Competition within the antenna industry has focused attention on dual band capability within a single antenna, minimization of antenna size, materials and manufacturing costs.
Therefore, it is an object of the invention to provide an antenna, which overcomes deficiencies in the prior art.